1. Field of the Invention
The invention generally relates to a delta-sigma modulator applied in a touch control detection system and a modulating method thereof, and more particularly, to a delta-sigma modulator capable of adjusting a center frequency of a noise transfer function (NTF) thereof and it's modulating method.
2. Description of Related Art
In the field of conventional art, it is generally required to include an anti-aliasing filter (AAF) in an analog to digital converter for lowering interference of high frequency noise in a system. The anti-aliasing filter is usually a one-stage or multiple-stage active or passive low-pass filter. If under a condition of adopting an analog to digital converter of low-pass delta-sigma modulation, then a low pass filtering effect may be achieved with the characteristics of a loop filter of the analog to digital converter itself.
When being applied to a touch system, a low frequency noise signal with a frequency band lower than 300 KHz would appear. If the conventional analog to digital converter of low-pass delta-sigma modulation is to be used for filtering out the low frequency noise signal, then a circuit design thereof would become even more complicated, and an area required for circuit layout would be substantially increased. Moreover, power consumption required by the analog to digital converter would also substantially be increased.